1. Field of the Invention
This invention relates to a process for preparing 2-carboxydibenzoylmethanes and more particularly, to a process for preparing 2-carboxydibenzoylmethanes which are useful as an inhibitor of the root geotropic response in plants or a growth regulator for plants, or a stabilizer for halogen-containing resins.
2. Description of the Prior Art
2-Carboxydibenzoylmethanes have high utility as an inhibitor of the root geotropic response in plants such as a cress and ryegrass seedling and a growth regulator for plants as discussed in detail by B. T. Brown [Experientia, 28, 1290 (1972); Pesticide science, 4, 473 (1973)]. It is also known that various derivatives from starting 2-carboxydibenzoylmethanes are useful as a growth regulator for plants [DE-OS No. 2600655 (1976)].
On the other hand, 2-carboxydibenzoylmethanes are known to be useful as a stabilizer for halogen-containing resins [U.S. Pat. No. 4381360 (1983) and Japanese Laid-open Patent Application No. 56-99254].
For the preparation of these compounds, there is known a process in which phthalic diesters and acetophenones are subjected to condensation reaction in the presence of bases. ##STR2##
However, the above process is disadvantageous in that 2-acylindane-1,3-dione is produced as by-product at a yield of 20 to 40% and the yields of the intended 2-carboxydibenzoylmethanes are as low as 20 to 50%.